By Azel Swemmer, Technical Director, Food and Drug Assurance Laboratories (Pty) Ltd
Chemical residues in food—resulting from the use of veterinary pharmaceuticals, agricultural pesticides, feed additives, and environmental contaminants—pose a significant risk to public health and food safety. These substances may persist in edible tissues, milk, eggs, and other animal-derived products if proper withdrawal periods and good agricultural practices are not adhered to. As in many jurisdictions, the regulation and surveillance of chemical residues in South Africa are essential for ensuring consumer protection, maintaining export market access, and fostering confidence in the national food supply chain. Robust analytical monitoring, guided by both domestic legislation and international frameworks such as Codex Alimentarius, is necessary to confirm compliance with established Maximum Residue Limits (MRLs) and to minimize the risks associated with chronic dietary exposure. Chemical residues refer to trace amounts of substances that remain in food products following the application of pesticides, administration of veterinary medicines, or exposure to environmental and industrial pollutants. These residues can enter the food chain during primary production, animal husbandry, feed management, or through post-harvest contamination during processing, storage, or transport. If not properly managed, such residues may accumulate and pose toxicological risks, particularly with repeated or long-term exposure. An effective chemical residue monitoring program must be grounded in comprehensive risk assessment. It should consider a wide spectrum of potential contaminants, including veterinary drugs used during animal production, pesticides applied to feed crops, fungicides used to suppress mycotoxins, and the mycotoxins themselves. In addition, residues of heavy metals in animal diets and persistent environmental contaminants—such as DDT (dichloro-diphenyl-trichloroethane) and PCBs (Polychlorinated Biphenyl compounds)—must be considered, particularly in regions where such substances may still be present. A scientifically sound monitoring strategy must therefore extend beyond commonly used inputs to reflect the full range of potential hazards in the production environment.
Regulatory Framework in South Africa
South Africa operates under a multi-agency food safety regulatory system:
• The Department of Agriculture, Land Reform and Rural Development (DALRRD) is responsible for regulating food of animal origin, including meat, milk, and eggs.
• The Department of Health, through the Foodstuffs, Cosmetics and Disinfectants Act (Act 54 of 1972), sets limits for chemical contaminants in food products.
• The Department of Trade, Industry and Competition (DTIC), along with the National Regulator for Compulsory Specifications (NRCS), plays a role in establishing and enforcing national food safety standards. A key regulatory mechanism in managing chemical residues is the Maximum Residue Limit (MRL) framework. MRLs specify the highest permissible concentration of a chemical residue in food, based on risk assessments conducted by international bodies such as the Codex Alimentarius Commission. In cases where local residue data is lacking, South Africa adopts Codex MRLs. These values are legally enforced under the Fertilizers, Farm Feeds, Agricultural Remedies and Stock Remedies Act (Act 36 of 1947). Where no MRL is specified for a particular compound or animal species, a default limit of 0.010 mg/kg is applied.
All registered veterinary medicinal products are required to include a package insert that specifies the legally mandated withdrawal period before slaughter or harvesting. In the case of compounded products, the onus lies with the veterinarian to retain supporting documentation indicating the appropriate withdrawal period. V-Tech has been a leader in conducting residue monitoring to support withdrawal times in food-producing animals and the veterinarians prescribing these medications. However, residues resulting from off-label drug use, easily accessible stock remedies, pesticides, and poor compliance practices—especially in informal or small-scale farming operations—continue to present regulatory challenges. Analytical testing for veterinary drug residues involves two main categories: screening and confirmatory methods. Screening techniques are valuable in routine monitoring, particularly for detecting known substances or high-risk drug classes. However, they often lack the specificity required for definitive identification and regulatory enforcement.
Confirmatory techniques—especially Liquid Chromatography–Tandem Mass Spectrometry (LC-MS/MS) and Gas Chromatography–Tandem Mass Spectrometry (GC-MS/MS)—are recognized globally as the gold standard for residue analysis in biological matrices. These methods provide superior sensitivity and selectivity, enabling the precise identification and quantification of a broad range of compounds. Modern residue laboratories can screen for over 140 individual drugs in a single analytical run, significantly improving the efficiency and scope of monitoring programs. The reliability of analytical results depends on the laboratory’s adherence to internationally accepted quality standards. ISO/IEC 17025 accreditation serves as a benchmark of technical competence and quality assurance. Accredited laboratories are required to validate their methods, calibrate instruments, ensure staff competency, and maintain robust data integrity systems.
For laboratories involved in food safety, environmental testing, or pharmaceutical analysis, ISO 17025 accreditation enhances credibility, facilitates regulatory acceptance, and supports international trade by demonstrating compliance with globally recognised standards. As both an importer and exporter of food products, South Africa must comply with international residue regulations to maintain access to global markets. Countries such as the European Union, United Arab Emirates, and China impose strict residue control requirements. Exporters must adhere to the specific residue monitoring programs of the importing country, which may include substances not routinely monitored in South Africa and emerging contaminants such as PFAS (per- and polyfluoroalkyl substances). In recent years, the private sector—including independent laboratories and major retail chains—has become increasingly involved in food safety initiatives. Retailers often implement their own residue testing programs to protect brand integrity, comply with internal risk protocols, and satisfy consumer expectations. These programs typically include farm-level traceability, regular audits, comprehensive residue screening, and data-driven supplier oversight. Food safety, particularly regarding chemical residues, is a shared responsibility that requires coordinated action across regulatory bodies, industry stakeholders, laboratories, and producers.
While South Africa has a robust regulatory framework, continuous improvement in risk-based monitoring, laboratory capacity, and enforcement is vital to address evolving challenges. By fostering collaboration and maintaining scientific and regulatory excellence, South Africa can safeguard public health and sustain its role in the global food trade.